The present invention generally relates to broadband and VDSL based communication networks having combined broadband and narrowband services, and more particularly to customer interface device capable of allowing a single twisted-pair copper cable to support both narrow and broadband services.
VDSL (Very high speed Digital Subscriber Line) is a packet-based transmission architecture used to provide extremely high bandwidth distribution of digital video and data signals to customer buildings. A VDSL-based architecture can advantageously provide a single platform for supporting bandwidth-intensive applications, such as Internet access, remote LAN access, video conferencing, and video-on-demand.
VDSL services are typically implemented in an asymmetric form having a downstream transmission capability of about 52 Mbps over twisted pair copper wire arranged in local loops of 300 m, 26 Mbps at 1,000 m, and 13 Mbps at 1,500 m. Upstream data rates in asymmetric implementations tend to range from about 1.6 Mbps to about 2.3 Mbps. A typical distribution network includes a central office equipped with a host digital terminal (HDT) and arranged to operate as hub between multiple video information providers (VIPs) and digital service providers (DSPs) and customer residential dwellings. In a fiber-to-the-neighborhood (FTTN) type distribution network, optic fiber (e.g. OC-3c and OC-12c) lines are used to connect the central office to a universal system access multiplexer (USAM), which is then connected to a network interface device (NID) located on the customer property via twisted pair copper wire. A dedicated VDSL loop extends between the NID and an individual customer residence using an existing POTS or telephone system twisted pair wire, and a customer interface device, such as a residential gateway or set top box, provides a connection point for a customer television or personal computer. A fiber-to-the-curb (FTTC) type distribution network is similar except that a broadband network unit (BNU) is used in place of the USAM, and coaxial cable is used to connect the BNU, NID, and set top box.
The VDSL signal format is used to carry signals to and from the customer. In these networks, the twisted pair copper wire is used to carry both narrowband and broadband signals. As a consequence, a signal splitter is required to separate the narrowband signals (such as telephone voice signals) and broadband signals for coupling to the existing copper-based wiring plant inside the residence. However, such an arrangement can be problematic in that the physical connection to the existing copper-based wiring plant allows introduction of electromagnetic interference (EMI) and radio interference into the distribution network. Such interference can easily degrade signal quality of the VDSL/broadband signals.
Therefore, a need exists for an economical arrangement which can be used in a VDSL distribution network to allow a single twisted pair wire to support both narrowband and broadband signals to and from a customer location while preventing ingress of unwanted interference into the network.
Therefore, it is an object of the present invention to provide an interface device which is coupled to a VDSL communication network and is capable of supporting narrowband and broadband signals on a common twisted-pair copper line while minimizing the possibility of noise from feeding back into the VDSL network through the device.
It is another object of the present invention to provide a customer interface device for use in a VDSL communication network which includes a narrowband and broadband signal splitter coupled to a low pass and high pass filter so that a common twisted-pair copper line can carry both narrowband and broadband signals while blocking infiltration of EMI and other noise into the VDSL network.
In accordance with these and other objects, the present invention provides an interface device located at a customer site for connection to a VDSL based communication network providing combined narrowband and broadband signals, where the interface device includes a network port for receiving the combined narrowband and broadband signals from a single twisted-pair copper cable connected to a network device, a narrowband port for connection to a wiring plant located at the customer site, and a broadband port for connection to a twisted-pair copper cable located at the customer site. A frequency splitter is connected to the network port for separating the broadband signals for output at the broadband port and the narrowband signals for output at the narrowband port. A low pass filter is connected between the frequency splitter and the narrowband port for filtering the separated narrowband signals before output at the narrowband port, and a high pass filter is connected between the frequency splitter and the broadband port for filtering the separated broadband signals before output at the broadband port. In addition to improving signal quality, the low pass filter and high pass filter reduce feedback of interference into the network from the wiring plant and the twisted-pair copper cable coupled to the broadband port.
In a preferred embodiment, the broadband port is connected to a Category 5 type twisted-pair copper cable to reduce signal interference with the separated and filtered broadband signals.
In accordance with another aspect of the present invention, a broadband communication network is provided for distributing combined narrowband and broadband signals, wherein the network includes a central office connected to at least one multi-media service provider and to a switched telephone system. The central office comprises narrowband and broadband signal processors for combining the narrowband and broadband signals on a single network distribution line. A network device is connected to the central office for providing a single twisted-pair copper cable drop feed to a customer site. An interface device is located at the customer site for receiving the combined narrowband and broadband signals from the single twisted-pair copper cable drop feed, wherein the interface device includes a frequency splitter for separating the broadband signals and narrowband signals for output on separate wiring plants located at the customer site, a low pass filter connected to the frequency splitter for filtering the separated narrowband signals before output from the interface device, and a high pass filter connected to the frequency splitter for filtering the separated broadband signals before output from the interface device.
The network can be configured as either a FTTC or FTTN type network with the network device comprising a universal service access multiplexer or a broadband network unit. The network is arranged so that the separated and filtered narrowband signals are output from the interface device on a copper pair wire, such as an existing telephone wiring plant at the customer site. The separated and filtered broadband signals are output from the interface device on a Category 5 twisted-pair copper cable.
In accordance with yet another aspect of the present invention, a method is provided for interfacing a customer site to a VDSL based communication network providing combined narrowband and broadband signals on a single distribution line, wherein the method includes receiving the combined narrowband and broadband signals at the customer site from a single twisted-pair copper drop feed, and splitting the narrowband and broadband signals into separate output signals. Then, the separated narrowband signals are low pass filtered, and the separated broadband signals are high pass filtered. The filtered signals are output on separate copper wiring plants located at the customer site for delivery to designated customer devices.
Thus, the present invention advantageously provides an interface device which can support delivery of narrowband and broadband signals on a common twisted-pair cable without compromising signal quality.